package com.vvv.designpattern.structualpatterns;

import java.sql.*;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicIntegerArray;

/**
 * @author vvv
 * @date 2023-10-21 15 36
 * discription 模拟数据库连接池，享元模式，使用Semaphore实现
 */
public class FlyweightSemaphore {
    public static void main(String[] args) {

    }
}
class Pool2 {
    // 连接池大小
    private final int poolSize;
    // 连接池
    private Connection[] connections;
    // 连接状态
    private AtomicIntegerArray status;

    private Semaphore semaphore;

    public Pool2(int poolSize) {
        this.poolSize = poolSize;
        connections = new Connection[poolSize];
        semaphore = new Semaphore(poolSize);
        status = new AtomicIntegerArray(new int[poolSize]);
        // 初始化连接池
        for (int i = 0; i < poolSize; i++) {
            connections[i] = new MockConnection2();
        }
    }

    public Connection borrow() {
        try {
            // 尝试拿许可，许可 - 1
            semaphore.acquire();
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        for (int i = 0; i < poolSize; i++) {
            // 如果没人用
            if (status.get(i) == 0) {
                // cas 如果status修改成功则可以borrow成功（因为status == 1 后其他线程是拿不了connection的
                if (status.compareAndSet(i, 0, 1)) {
                    return connections[i];
                }
            }
        }
        // 不会执行到这里，因为如果线程没有拿到许可则会被阻塞
        return null;
    }

    public void free(Connection connection) {
        // 判断connection是不是自己的
        for (int i = 0; i < poolSize; i++) {
            if (connections[i] == connection) {
                // 这里不用加锁，因为调用这个方法的肯定是connection的持有者
                status.set(i, 0);
                // 归还许可，许可 + 1
                semaphore.release();
                break;
            }
        }
    }
}
class MockConnection2 implements Connection {
    @Override
    public Statement createStatement() throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql) throws SQLException {
        return null;
    }

    @Override
    public String nativeSQL(String sql) throws SQLException {
        return null;
    }

    @Override
    public void setAutoCommit(boolean autoCommit) throws SQLException {

    }

    @Override
    public boolean getAutoCommit() throws SQLException {
        return false;
    }

    @Override
    public void commit() throws SQLException {

    }

    @Override
    public void rollback() throws SQLException {

    }

    @Override
    public void close() throws SQLException {

    }

    @Override
    public boolean isClosed() throws SQLException {
        return false;
    }

    @Override
    public DatabaseMetaData getMetaData() throws SQLException {
        return null;
    }

    @Override
    public void setReadOnly(boolean readOnly) throws SQLException {

    }

    @Override
    public boolean isReadOnly() throws SQLException {
        return false;
    }

    @Override
    public void setCatalog(String catalog) throws SQLException {

    }

    @Override
    public String getCatalog() throws SQLException {
        return null;
    }

    @Override
    public void setTransactionIsolation(int level) throws SQLException {

    }

    @Override
    public int getTransactionIsolation() throws SQLException {
        return 0;
    }

    @Override
    public SQLWarning getWarnings() throws SQLException {
        return null;
    }

    @Override
    public void clearWarnings() throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public Map<String, Class<?>> getTypeMap() throws SQLException {
        return null;
    }

    @Override
    public void setTypeMap(Map<String, Class<?>> map) throws SQLException {

    }

    @Override
    public void setHoldability(int holdability) throws SQLException {

    }

    @Override
    public int getHoldability() throws SQLException {
        return 0;
    }

    @Override
    public Savepoint setSavepoint() throws SQLException {
        return null;
    }

    @Override
    public Savepoint setSavepoint(String name) throws SQLException {
        return null;
    }

    @Override
    public void rollback(Savepoint savepoint) throws SQLException {

    }

    @Override
    public void releaseSavepoint(Savepoint savepoint) throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
        return null;
    }

    @Override
    public Clob createClob() throws SQLException {
        return null;
    }

    @Override
    public Blob createBlob() throws SQLException {
        return null;
    }

    @Override
    public NClob createNClob() throws SQLException {
        return null;
    }

    @Override
    public SQLXML createSQLXML() throws SQLException {
        return null;
    }

    @Override
    public boolean isValid(int timeout) throws SQLException {
        return false;
    }

    @Override
    public void setClientInfo(String name, String value) throws SQLClientInfoException {

    }

    @Override
    public void setClientInfo(Properties properties) throws SQLClientInfoException {

    }

    @Override
    public String getClientInfo(String name) throws SQLException {
        return null;
    }

    @Override
    public Properties getClientInfo() throws SQLException {
        return null;
    }

    @Override
    public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
        return null;
    }

    @Override
    public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
        return null;
    }

    @Override
    public void setSchema(String schema) throws SQLException {

    }

    @Override
    public String getSchema() throws SQLException {
        return null;
    }

    @Override
    public void abort(Executor executor) throws SQLException {

    }

    @Override
    public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {

    }

    @Override
    public int getNetworkTimeout() throws SQLException {
        return 0;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }
}
